<!doctype html><html><head>
    <title>A canvas clip example</title>
    <meta name="DC.creator" content="Kamiel Martinet, http://www.martinet.nl/">
    <meta name="DC.publisher" content="Mozilla Developer Center, http://developer.mozilla.org">

<script src="../uuCanvas.js"></script>

<script>
function xcanvas() {
    drawShape(document.getElementById('slcanvas'), 0, 1);
    drawShape(document.getElementById('vmlcanvas'), 0, 1);
    drawShape(document.getElementById('flashcanvas'), 0, 1);
}
function matrix() {
    drawShape(document.getElementById('slcanvas'), 1);
    drawShape(document.getElementById('vmlcanvas'), 1);
    drawShape(document.getElementById('flashcanvas'), 1);
}

var globalAlpha = 1.0;
function switchAlpha() {
    globalAlpha -= 0.2;
    drawShape(document.getElementById('slcanvas'));
    drawShape(document.getElementById('vmlcanvas'));
    drawShape(document.getElementById('flashcanvas'));
}

var lineWidth = 1.0;
function switchLineWidth() {
    lineWidth += 2;
    drawShape(document.getElementById('slcanvas'));
    drawShape(document.getElementById('vmlcanvas'));
    drawShape(document.getElementById('flashcanvas'));
}

function drawShape(canvas, matrix, first){
    if (!canvas.getContext){ return; }

    var ctx = canvas.getContext('2d');

    ctx.clear();
    if (matrix) {
        ctx.translate(-10, 5);
        ctx.scale(1.2, 0.8);
        ctx.rotate(5 * Math.PI / 180);
    }
    ctx.globalAlpha = globalAlpha;
    ctx.lineWidth = lineWidth;

    if (first) {
        ctx.fillRect(0,0,150,150);
        ctx.translate(75,75);
    }
    // Create a circular clipping path
    ctx.beginPath();
    ctx.arc(0,0,60,0,Math.PI*2,true);
    ctx.clip();

    // draw background
    var lingrad = ctx.createLinearGradient(0,-75,0,75);
    lingrad.addColorStop(0, '#232256');
    lingrad.addColorStop(1, '#143778');

    ctx.fillStyle = lingrad;
    ctx.fillRect(-75,-75,150,150);

    // draw stars
    for (var j=1;j<50;j++){
        ctx.save();
        ctx.fillStyle = '#fff';
        ctx.translate(75-Math.floor(Math.random()*150),75-Math.floor(Math.random()*150));
        drawStar(ctx,Math.floor(Math.random()*4)+2);
        ctx.restore();
    }
}

function drawStar(ctx,r){
    ctx.save();
    ctx.beginPath()
    ctx.moveTo(r,0);
    for (var i=0;i<9;i++){
        ctx.rotate(Math.PI/5);
        if(i%2 == 0) {
            ctx.lineTo((r/0.525731)*0.200811,0);
        } else {
            ctx.lineTo(r,0);
        }
    }
    ctx.closePath();
    ctx.fill();
    ctx.restore();
}
</script>
    <style type="text/css">
      body { margin: 20px; font-family: arial,verdana,helvetica; background: #fff;}
      h1 { font-size: 140%; font-weight:normal; color: #036; border-bottom: 1px solid #ccc; }
      canvas { border: 2px solid #000; float: left; margin-right: 20px; margin-bottom: 20px; }
      pre { float:left; display:block; background: rgb(238,238,238); border: 1px dashed #666; padding: 15px 20px; margin: 0 0 10px 0; }
    </style>
  </head>
  <body>
    <h1>A canvas <code>clip</code> example</h1>
    <div>
      <input type="button" value="matrix effect" onclick="matrix()" />
      <input type="button" value="alpha -0.2" onclick="switchAlpha()" />
      <input type="button" value="lineWidth +2" onclick="switchLineWidth()" />
      <br />
      <canvas id="slcanvas" class="sl" width="150" height="150"></canvas>
      <canvas id="vmlcanvas" class="vml" width="150" height="150"></canvas>
      <canvas id="flashcanvas" class="flash" width="150" height="150"></canvas>
      <pre>
function xcanvas() {
    draw(document.getElementById('slcanvas'));
    draw(document.getElementById('vmlcanvas'));
    draw(document.getElementById('flashcanvas'));
}
function matrix() {
    draw(document.getElementById('slcanvas'), 1);
    draw(document.getElementById('vmlcanvas'), 1);
    draw(document.getElementById('flashcanvas'), 1);
}

var globalAlpha = 1.0;
function switchAlpha() {
    globalAlpha -= 0.2;
    drawShape(document.getElementById('slcanvas'));
    drawShape(document.getElementById('vmlcanvas'));
    drawShape(document.getElementById('flashcanvas'));
}

var lineWidth = 1.0;
function switchLineWidth() {
    lineWidth += 2;
    drawShape(document.getElementById('slcanvas'));
    drawShape(document.getElementById('vmlcanvas'));
    drawShape(document.getElementById('flashcanvas'));
}

function draw(canvas, matrix){
    if (!canvas.getContext){ return; }

    var ctx = canvas.getContext('2d');

    ctx.clear();
    if (matrix) {
        ctx.translate(-10, 5);
        ctx.scale(1.2, 0.8);
        ctx.rotate(5 * Math.PI / 180);
    }
    ctx.globalAlpha = globalAlpha;
    ctx.lineWidth = lineWidth;

    ctx.fillRect(0,0,150,150);
    ctx.translate(75,75);
    // Create a circular clipping path
    ctx.beginPath();
    ctx.arc(0,0,60,0,Math.PI*2,true);
    ctx.clip();

    // draw background
    var lingrad = ctx.createLinearGradient(0,-75,0,75);
    lingrad.addColorStop(0, '#232256');
    lingrad.addColorStop(1, '#143778');

    ctx.fillStyle = lingrad;
    ctx.fillRect(-75,-75,150,150);

    // draw stars
    for (var j=1;j<50;j++){
        ctx.save();
        ctx.fillStyle = '#fff';
        ctx.translate(75-Math.floor(Math.random()*150),75-Math.floor(Math.random()*150));
        drawStar(ctx,Math.floor(Math.random()*4)+2);
        ctx.restore();
    }
}

function drawStar(ctx,r){
    ctx.save();
    ctx.beginPath()
    ctx.moveTo(r,0);
    for (var i=0;i<9;i++){
        ctx.rotate(Math.PI/5);
        if(i%2 == 0) {
            ctx.lineTo((r/0.525731)*0.200811,0);
        } else {
            ctx.lineTo(r,0);
        }
    }
    ctx.closePath();
    ctx.fill();
    ctx.restore();
}
      </pre>
    </div>
  </body>
</html>
